Pump

ABSTRACT

The invention relates to a pump that has a housing with a recess in which a pump unit is situated. The pump unit has a pump chamber formed from a pump chamber ring and at least one pressure plate situated on the pump chamber ring, and a rotary-drivable pump element situated in the pump chamber. The pump unit has a pressure space which is delimited by the recess and the pressure plate. The invention provides that a circumferential distancing means is situated between the bearing surfaces of the pump chamber ring and the pressure plate on the pressure space side, or the radial extension of the pump chamber ring is chosen to be less than the radial extension of the pressure plate on the pressure space side.

RELATED APPLICATIONS

[0001] The present application is a U.S. National Phase of PCT/EP01/06290, filed Jun. 1, 2001 claiming priority to German Patent Application No. 10027811.6, Filed Jun. 5, 2000.

BACKGROUND

[0002] The invention relates to a pump that has a housing with a recess in which a pump unit is situated. The pump unit has a pump chamber formed from a pump chamber ring and at least one pressure plate situated on the pump chamber ring, and a rotary-drivable pump element situated in the pump chamber. The pump unit has a pressure space which is delimited by the recess and the pressure plate.

[0003] Pumps of the aforementioned type are known. To counteract warping of the pressure plate on the pressure space side, a pressure plate of the prior art has a particularly rigid design. This known pressure plate thus has a relatively large material thickness, which correspondingly increases the size of the pump. However, in the past this has been accepted in order to keep the leak opening between the pressure plate on the pressure space side and the pump element as small as possible, and to achieve an adequate volumetric efficiency of the pump.

[0004] It is also known from German Patent Application 199 00 927 A1 to support the pressure plate on the pressure space side against the base of the recess provided in the housing, using a distancing means. In addition, to reduce the size of the leak opening between the pressure plate situated at the base of the recess and the pump element, the entire pump element must be mounted in a floating manner in the axial direction.

SUMMARY OF THE INVENTION

[0005] The object of the invention, therefore, is to provide a pump of the aforementioned type which has a simple design and yet has a good volumetric efficiency.

[0006] This object is achieved using a pump that has a housing in which a recess is provided. In the recess a pump unit is situated, which has a pump chamber formed from a pump chamber ring and at least one pressure plate situated on the pump chamber ring, and a rotary-drivable pump element, which is situated in the pump chamber. In addition, the pump has a pressure space, which is delimited by the recess and the pressure plate. According to the invention, the pump is characterized by the fact that a circumferential distancing means is situated between the bearing surfaces of the pump chamber ring and the pressure plate on the pressure space side. The impingement of the media pressure on the side face of the pressure plate facing the pressure space creates on the one hand a force on the ellipsoidal or circular surface of the pressure plate on the pressure space side, which is located directly opposite from the through opening in the pump chamber ring; on the other hand, a force created by the media pressure acts on the annular surface of the pressure plate on the pressure space side, so that a counterforce is created which counteracts the deflection of the pressure plate in the region of the circular surface. Consequently, according to the invention the deflection of the pressure plate in the pump is reduced at least so that the leak opening in the pump, once adjusted—even during operation and thus under the effect of pressure, temperature, and so forth—remains essentially unchanged. This allows the leak opening to be chosen to be correspondingly tight or narrow, thereby improving the volumetric efficiency of the pump. Since the deflection of the pressure plate is substantially compensated for, this pressure plate need not be designed to be particularly strong, thus allowing the axial length of the pump to be reduced.

[0007] This object is also achieved by a pump in which, instead of the circumferential distancing means, according to the invention the radial extension of the pump chamber ring is chosen to be less than the radial extension of the pressure plate on the pressure space side. Thus, the pressure plate projects above the outer circumferential surface of the pump chamber ring, so that once again, as previously mentioned, the radially outwardly extending annular surface of the pressure plate is acted on by a force which counteracts the deflection of the pressure plate in the vicinity of the circular region of the pressure plate situated opposite from the through opening. As a result, the volumetric efficiency is also improved for this pump designed according to the invention, since a very small leak opening can be chosen.

[0008] To seal the pressure space with respect to the remaining recess area, a circumferential seal is provided between the side wall of the recess in the housing and the pressure plate on the pressure space side. This circumferential seal is thus situated between the side wall of the recess and the lateral face of the pressure plate. However, this also ensures that the cavity located below the pressure plate and between the pump chamber ring and the pressure plate ring surface is not acted on by the media pressure.

[0009] A particularly preferred exemplary embodiment of the invention is characterized by the fact that the distancing means is constructed as one piece with the pump chamber ring and/or the pressure plate on the pressure space side. Using appropriate manufacturing methods, for example methods for conveying cuttings, the distancing means may be easily manufactured as one piece with the pump chamber ring or the pressure plate. According to the invention the pump is thus economical to manufacture, and at the same time the volumetric efficiency is improved.

[0010] In one exemplary embodiment, the pressure space is situated between the pressure plate on the pressure space side and the base of the recess.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The invention is described in more detail below based on exemplary embodiments, with reference to the drawings. They show:

[0012]FIG. 1 shows a first exemplary embodiment of a pump;

[0013]FIG. 2 shows a second exemplary embodiment of a pump;

[0014]FIG. 3 schematically shows the inventive support of the pressure plate of a pump on the pressure space side; and

[0015]FIG. 4 shows a third exemplary embodiment of a pump.

DETAILED DESCRIPTION

[0016] The pump described below may be designed as a vane pump, lobe pump, or roller pump, in which the rotary-drivable pump element is formed by a rotor, and in which vanes or rollers are used, depending on the type of pump, or, when the design is a lobe pump, is achieved as a profile element. However, it is also possible to design the pump as a gear pump. Such pumps and their function are generally known, so that in the following description the exact design of the rotary-drivable pump element is not described in further detail.

[0017]FIG. 1 shows a greatly simplified and only partially illustrated pump 1 in cross section, which is enclosed by a housing 2. In this housing 2 a recess 3 is provided, which is closed by a housing lid (not shown here), which is attachable to housing 2 of pump 1.

[0018] A pump unit 4 is situated in recess 3, which has a pump chamber 5 that is delimited by a pump chamber ring 6 and two pressure plates 9 and 10 situated on annular bearing surfaces 7 and 8 of the pump chamber ring. Instead of pressure plate 9, housing 2 may also be designed in such a way that the housing delimits pump chamber 5.

[0019] However, pressure plate 10 is provided, at a minimum. One of pressure plates 10 is situated at a distance from base 11 of substantially cylindrical recess 3. Together with recess 3, this pressure plate 10 forms a pressure space 12 into which the medium conveyed by a rotary-drivable pump element is introduced. Pressure space 12 has a connection to a pump-side user connector (not shown here). Rotary-drivable pump element 13 is a rotor, as mentioned above, of a vane pump, lobe pump, or roller pump, or a gear of a gear pump. To enable pump element 13 to operate by rotary drive, the pump element is situated in a rotationally fixed manner on one end 14 of a drive shaft 15 rotatably mounted in housing 2. A driving torque may be introduced at the other end of the drive shaft (not shown here).

[0020] Drive shaft 15 passes through pressure space 12 and penetrates an opening 16 provided, preferably centrally, in pressure plate 10. A circumferential sealing element 17 is situated inside opening 16. The seal is achieved by means of a sealing gap. It is preferable to also provide a sealing element between the lateral surface of drive shaft 15 and drive shaft opening 18 formed in housing 2 in order to seal off pressure space 12 from the outside, as does sealing element 17. This sealing element may be designed as a radial shaft sealing ring 16′.

[0021] Between bearing surface 7 provided on pump chamber ring 6 and oppositely situated bearing surface 18′ of pressure plate 10 on the pressure space side a circumferential distancing means 19 is provided, which in the present exemplary embodiment according to FIG. 1 is constructed as one piece with pump chamber ring 6. For this purpose a circumferential, radially outwardly extending groove 20 which is preferably open-edged is introduced into end face 7′ of pump chamber ring 6, so that a cavity 21 is formed at least in part between pressure plate 10 and pump chamber ring 6. Distancing means 19 is positioned on pump chamber ring 6 in such a way that the distancing means divides pressure plate surface 22 facing pump chamber ring 6 into two sections: circular or ellipsoidal surface 24 of the pressure plate situated facing opening 23 in pump chamber ring 6, and radially outwardly extending annular surface 24′ of the pressure plate. Circular or ellipsoidal surface 24 of the pressure plate is thus situated in circular or ellipsoidal area 24″, whereas annular surface 24′ of the pressure plate is situated in annular area 24′″ of pressure plate 10. Distancing means 19 is situated at a distance from side wall 25 of recess 3. An ellipsoidal surface of the pressure plate results when opening 23 essentially has the shape of an ellipse. Pump element 13 then preferably has a rotational axis containing the midpoint of the ellipse. However, opening 23 may also have a circular cross section, in which case the pump element has a rotational axis that is offset from the midpoint of opening 23. FIG. 1 shows that a circumferential seal 27 is provided between side wall 25 and border surface 26 of pressure plate 10 which preferably comes to rest in an annular groove 28, which in the illustrated exemplary embodiment is introduced into border surface 26. However, seal 27 could also be positioned in an annular groove to be produced in housing 2, the annular groove thus being provided in side wall 25 of recess 3.

[0022]FIG. 2 shows a second exemplary embodiment of a pump 1. In FIG. 2, parts in sectionally illustrated pump 1 which are the same or which have the same function are provided with the same reference numbers as in FIG. 1. Therefore, the following discussion is concerned only with differences between pump 1 as shown in FIG. 1 and in FIG. 2. In pump 1 according to FIG. 2, distancing means 19 is constructed as one piece with pressure plate 10 on the pressure space side, thus forming a prominence on pressure plate surface 22. To this end, a radially outwardly extending annular groove 29, preferably open-edged, in annular region 24′″ is introduced into this pressure plate surface 22, so that distancing means 19 (seen in a top view) is designed as a flat circular disk. Distancing means 19 may also be provided as a separate insert part which then comes to rest between pressure plate 10 and pump chamber ring 6.

[0023]FIG. 4 shows a third exemplary embodiment of a pump 1. As in FIGS. 1 and 2, parts which are the same or which have the same function are provided with the same reference numbers, so that reference may be made to the descriptions already given. In contrast to the exemplary embodiments according to FIGS. 1 and 2, pump chamber ring 6 is not supported on side wall 25 of recess 3, but instead is held centered on pressure plate 9. Connecting elements 31 or centering pins may be provided for this purpose, and may be designed as connecting pins. These connecting elements 31 may also be provided between pump chamber ring 6 and pressure plate 9 and—in a shape that does not hinder deflection of pressure plate 10—also between pump chamber ring 6 and pressure plate 10 on the pressure space side. Such connecting elements 31 may also be used in pumps 1 according to FIGS. 1 and 2.

[0024] The radial extension, in particular outer diameter A of pump chamber ring 6, in the exemplary embodiment of pump 1 according to FIG. 4 is thus less than the radial extension of, for example, outer diameter B of pressure plate 10 on the pressure space side.

[0025] The operating principle of distancing means 19 according to the invention and the support of pressure plate 10 according to FIG. 4 are described in more detail below, with reference to FIG. 3. In FIG. 3, pump 1 is further simplified and is illustrated only schematically. Parts which are the same or which have the same function are provided with the same reference numbers as in FIGS. 1, 2, and 4. During operation of pump 1, the medium conveyed in pressure space 12 via pump element 13 has a pressure p. Forces K thus act on outer surface 32 of the pressure plate facing base 11, said forces pushing pressure plate 10, in its circular region 24″ facing opening 23 of pump chamber ring 6, in the direction of rotary-drivable pump element 13. Forces K′ act radially outward, and thus in annular region 24′″ of pressure plate surface 32, with the same direction of action as forces K, but in pressure plate 10 forces K′ cause a counter-deflection of pressure plate 10 within circular region 24′″, so that the bulging of pressure plate 10 in the direction of pump element 13 is reduced. In contrast, annular region 24′″ of pressure plate 10 which extends radially outward according to distancing means 19 is pushed into cavity 21. The deflections caused by forces K and K′ overlap, so that the resulting deflection of pressure plate 10 is at least reduced.

[0026] The bulging resulting from deflection of the pressure plate in the circular region appears in known pumps due to the fact that regions having different media pressures are present within the pump chamber, since within pump chamber 5 at least one pressure area and one suction area are formed in which different media pressures prevail, so that forces acting on the pressure plate surface in the circular region cannot be compensated for solely by the forces resulting from the media pressures.

[0027] By providing distancing means 19 according to the invention in pump 1, pressure forces K″ from pump chamber 5 acting on pressure plate surface 22 are supported by forces K′ acting on annular surface 24′ of the pressure plate, so that undesired deflection of pressure plate 10 is avoided for the particular use. Thus, even during operation of pump 1, the leak opening between circular surface 24 of the pressure plate and pump element 13 is essentially unchanged. It is therefore possible for the leak opening to have a very narrow design, thereby improving the volumetric efficiency of pump 1.

[0028] Thus, in the absence of distancing means 19, the bulging of pressure plate 10 would occur as the result of the unsymmetrical exertion of pressure by forces K″ on circular surface 24 of the pressure plate and on the surface region of pressure plate 10 facing base 11 on which forces K act.

[0029] However, by means of distancing means 19 which acts as a rocking edge 33 for pressure plate 10 situated thereon, or, as illustrated in FIG. 4, the smaller radial extension A of pump chamber ring 6 with respect to radial extension B of pressure plate 10, a counterbending moment is created which counteracts the bending moment produced by exertion of force K. This counterbending moment creates a deformation which counteracts the bending deformation of radially inwardly extending circular region 24″ of pressure plate 10 resulting from pressure force K, thus supporting prevailing forces K″ from pump chamber 5. The overall result is that the provision of rocking edge 33 reduces the deflection of pressure plate 10. It is clear that by the choice of outer diameter A (FIG. 4) of pump chamber ring 6, lever arm 34 (FIG. 3) on pressure plate 10 situated between side wall 25 and rocking edge 33 may be varied in length L to alter the counterbending moment, in particular for the adjustment of pressure conditions in pressure chamber 12 and in pump chamber 5. If pump chamber ring 6 rests with its outer circumferential surface against side wall 25, as shown in FIGS. 1 and 2, length L of lever arm 34 on pressure plate 10 may be adjusted by setting an appropriate distance of distancing means 19 from side wall 25.

[0030] The patent claims submitted with the application represent recommended wording, without prejudice to further patent protection. The applicant reserves the right to claim further combinations of features thus far described only in the description and/or in the drawings.

[0031] References used in the subclaims indicate the further development of the subject of the main claim through the features of the particular subclaim; said references are not to be construed as a renunciation of independent, objective protection for the combinations of features of the referenced subclaims.

[0032] Since, with respect to the prior art in existence on the priority date, unique and independent inventions may be formed from the subjects of the subclaims, the applicant reserves the right to make these the subject of independent claims or declarations of division of the application. The subjects of the subclaims may also comprise independent inventions which have an organization which is independent of the subjects of the preceding subclaims.

[0033] The exemplary embodiments are not to be construed so as to limit the invention. Rather, numerous alterations and modifications are possible within the scope of the present invention, in particular such variations, elements, and combinations and/or materials which, for example by combination or modification of individual features or elements or procedural steps described in connection with the general description and embodiments as well as the claims, and in the drawings, may be deduced by those skilled in the art with regard to the approach to the inventive object and which by combinable features result in a new subject or in new procedural steps or consequences of procedural steps, as well as to the extent that they affect the manufacturing, testing, and operating methods. 

1. Pump that has a housing with a recess in which a pump unit is situated which has a pump chamber formed from a pump chamber ring and at least one pressure plate situated on the pump chamber ring, and a rotary-drivable pump element situated in the pump chamber, and has a pressure space which is delimited by the recess and the pressure plate, characterized in that a circumferential distancing means is situated between the bearing surfaces of the pump chamber ring and the pressure plate on the pressure space side.
 2. Pump that has a housing with a recess in which a pump unit is situated which has a pump chamber formed from a pump chamber ring and at least one pressure plate situated on the pump chamber ring, and a rotary-drivable pump element situated in the pump chamber, and has a pressure space which is delimited by the recess and the pressure plate, characterized in that the radial extension of the pump chamber ring is less than the radial extension of the pressure plate on the pressure space side.
 3. Pump, in particular according to claim 1 or 2, characterized in that a circumferential seal is situated between the side wall of the recess in the housing and the pressure plate on the pressure space side.
 4. Pump, in particular according to claim 1 or 3, characterized in that the distancing means is constructed as one piece with the pump chamber ring and/or the pressure plate on the pressure space side.
 5. Pump, in particular according to claim 1 or 2, characterized in that the pressure space is situated between the base of the recess and the pressure plate on the pressure space side.
 6. Pump that has a housing with a recess in which a pump unit is situated which has a pump chamber formed from a pump chamber ring and at least one pressure plate situated on the pump chamber ring, and a rotary-drivable pump element situated in the pump chamber, and has a pressure space which is delimited by the recess and the pressure plate, characterized by at least one inventive feature disclosed in the application documents. 